A municipal water network is supplied by a central water tower. The free surface of the water inside the tower is maintained at a constant elevation of above sea level. The plumbing network is a closed, interconnected system, and the water is completely static.
Arrange the following four locations within this network in order from the LOWEST hydrostatic water pressure to the HIGHEST hydrostatic water pressure:
- 1A hilltop valve at an elevation of above sea level
- 2A second-floor residential tap at an elevation of above sea level
- 3A street-level fire hydrant at an elevation of above sea level
- 4A basement water main at an elevation of below sea level ()
Answer
The correct order from lowest pressure to highest pressure is: Hilltop valve, Second-floor residential tap, Street-level fire hydrant, and Basement water main.
In a closed, static fluid system, hydrostatic pressure is determined entirely by the depth of the fluid relative to its highest free surface. By calculating the depth of each location from the 50-meter water tower surface, we find that locations at higher absolute elevations have shallower water columns above them, resulting in lower pressure. Conversely, locations at lower elevations have deeper water columns and thus higher pressure. Therefore, ranking the locations from highest elevation to lowest elevation correctly orders them from lowest hydrostatic pressure to highest hydrostatic pressure.
Step-by-Step Solution
Key Concept
Hydrostatic pressure in communicating vessels depends solely on the depth of the fluid from the highest free surface, independent of the shape of the pipes.